Longitudinal Tracking of Physical Frailty and Health-Related Quality of Life Through Patient-Reported Outcome Measures in Adult Candidates on the Kidney Transplant Waiting List

Study Design and Framework This research employs a convergent-parallel mixed-methods design to evaluate frailty dynamics and patient-reported outcomes in Kidney Transplantation (KT) candidates. The quantitative component is a longitudinal observational study, while the qualitative component is grounded in Heideggerian hermeneutic phenomenology to explore the lived experience of patients during the waiting list period.

Quantitative Procedures and Data Collection Participants will be recruited during their initial KT evaluation at Hospital del Mar (Barcelona). Frailty will be assessed using the Fried Phenotype (assessing weight loss, exhaustion, physical activity, walk time, and grip strength) at baseline and subsequently every six months while the patient remains on the waiting list.

To monitor Patient-Reported Outcome Measures (PROMs), the study utilizes the Patient-Reported Outcomes Measurement Information System (PROMIS)-29 v2.0 questionnaire. This instrument covers seven health domains: physical function, anxiety, depression, fatigue, sleep disturbance, ability to participate in social roles/activities, and pain interference. Data collection will be performed via a digital platform (electronic PROMs [ePROMs]), allowing for real-time monitoring. For patients facing technological or language barriers, an Advanced Practice Nurse (APN) will provide support to ensure data completeness and minimize selection bias.

Qualitative Exploration A purposive sample of participants will undergo in-depth semi-structured interviews. These sessions will focus on the subjective meaning of frailty, the impact of the waiting period on daily life, and the experience of using digital health tools. Interviews will be audio-recorded, transcribed verbatim, and analyzed using thematic analysis to identify core existential themes.

Quality Assurance and Data Management • Data Validation: A data dictionary has been developed, defining each variable, its source, and acceptable ranges to ensure consistency. • Source Data Verification: Data entered into the electronic Case Report Form (eCRF) will be cross-referenced with electronic medical records to ensure accuracy. • Standard Operating Procedures (SOPs): Specific SOPs are in place for patient recruitment, the standardized administration of physical performance tests (e.g., handgrip strength using a dynamometer), and the management of technical issues with the ePROM platform.